A market or industry controlled by exactly two companies or producers, with little competition from others.
From duo- (Latin 'two') + -poly (from Greek polein 'to sell'). The term was coined in early 20th-century economics as a variant of monopoly to describe two-firm markets.
The classic example is Coke and Pepsi—they spend billions fighting over market share, but neither has an incentive to really compete on price, so they basically split the market and both prosper, which is the dirty secret of duopolies.
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